TW202207381A - Copper base substrate - Google Patents

Abstract

A copper base substrate of the present invention comprises a copper substrate, an insulating layer, and a circuit layer that are stacked in this order. The ratio of the thickness (unit: [mu]m) with respect to the modulus of elasticity (unit: GPa) at 100 DEG C of the insulating layer is at least 50. The circuit layer has the modulus of elasticity of 100 GPa or less at 100 DEG C.

Description

Copper base substrate

The present invention relates to a copper base substrate. The present invention claims priority based on Japanese Patent Application No. 2020-065163 filed on March 13, 2020, the content of which is incorporated herein by reference.

A metal base substrate is known as one of the substrates for mounting electronic components such as semiconductor elements and LEDs. The metal base substrate is a laminate in which a metal substrate, an insulating layer, and a circuit layer are laminated in this order. The insulating layer is generally formed of an insulating composition containing a resin having excellent insulating properties or withstand voltage and an inorganic filler having excellent thermal conductivity. Electronic components are mounted on the circuit layer by soldering. In the metal base substrate thus constituted, the heat generated by the electronic components is transmitted to the metal substrate through the insulating layer, and is dissipated from the metal substrate to the outside.

Among the metal substrate substrates, when the thermal expansion rate of the metal substrate substrate and the electronic components joined by soldering on the metal substrate substrate is greatly different, the cooling and heating cycles caused by the opening/closing of the electronic components or the external environment are used in the bonding. The stress imparted by the soldering of the circuit layer of electronic components and metal substrate substrates will increase, so that solder cracks may occur. For this reason, there is a review plan to reduce the elastic modulus of the insulating layer of the metal base substrate, and to reduce the difference in thermal expansion coefficient between the metal substrate and the electronic component via the metal base substrate with the insulating layer (Patent Documents 1 and 2). ). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-87866 [Patent Document 2] Japanese Patent Laid-Open No. 2016-111171

[The problem to be solved by the invention]

Suppresses the generation of solder cracks caused by the cooling and heating cycle when installing electronic components. In order to improve the reliability of the cooling and heating cycle, by reducing the elastic modulus of the insulating layer of the metal substrate substrate, it is easy to deform the insulating layer and effectively alleviate the expansion of the metal substrate. caused by thermal stress. However, due to the stress on the solder caused by the expansion of the circuit layer, only the elastic modulus of the insulating layer of the metal base substrate is reduced, and there is a limit to improving the reliability of the cooling and heating cycle.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a metal base substrate excellent in reliability with respect to a cooling and heating cycle when mounting electronic components. [Means for solving problems]

In order to solve the above-mentioned problems, the metal base substrate of the present invention is a copper base substrate in which a copper substrate, an insulating film, and a circuit layer are laminated in this order, wherein the insulating layer is a ratio of the elastic modulus (unit: GPa) to 100°C. The ratio of the thickness (unit: μm) is 50 or more, and the elastic modulus of the circuit layer at 100° C. mentioned above is 100 GPa or less.

According to the copper base substrate of the present invention, since the ratio of the thickness (unit: μm) of the insulating layer to the modulus of elasticity (unit: GPa) at 100° C. is greater than 50, the insulating layer is easily deformed, and the cycle of cooling and heating can be changed. The resulting difference in thermal expansion between the metal substrate and the electronic components is mitigated by an insulating layer. In addition, since the elastic modulus of the circuit layer at 100°C is as low as 100GPa or less, the difference between the thermal expansion coefficients of the circuit layer and the electronic components caused by the cycle of cooling and heating can be reduced. Therefore, through the cycle of cooling and heating, the stress applied to the solder of the circuit layer that joins the electronic component and the copper base substrate can be reduced. Therefore, the copper base substrate of the present invention improves the reliability of the cooling and heating cycles when mounting electronic components.

Here, in the copper base substrate of the present invention, the insulating layer may include polyimide resin, polyimide resin, or a mixture of these resins. At this time, since the insulating layer contains these resins, the insulating properties, voltage resistance, chemical resistance and mechanical properties of the copper base substrate are improved.

In addition, in the copper base substrate of the present invention, the insulating layer contains an inorganic filler, and the average particle size of the inorganic filler can be in the range of 0.1 μm or more and 20 μm or less. At this time, since the insulating layer contains the above-mentioned inorganic filler, the thermal conductivity and withstand voltage of the copper base substrate are improved.

Furthermore, in the copper base substrate of the present invention, the circuit layer may be made of copper foil, copper alloy foil, aluminum foil, or aluminum alloy foil. At this time, since the circuit layer is made of copper foil, copper alloy foil, aluminum foil or aluminum alloy foil, the circuit layer can be thinned due to high conductivity. [Inventive effect]

According to the present invention, it is possible to provide a copper base substrate excellent in reliability with respect to cooling and heating cycles when mounting electronic components.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a schematic cross-sectional view of a copper base substrate according to an embodiment of the present invention. In FIG. 1, the copper base substrate 10 is a laminate in which the copper substrate 20, the insulating layer 30, and the circuit layer 40 are laminated in this order. On the circuit layer 40 of the copper base substrate 10 , the terminals 61 of the electronic components 60 are mounted by the solder 50 .

The copper substrate 20 is a member that becomes the basis of the copper base substrate 10 . The copper substrate 20 is made of copper or copper alloy.

The insulating layer 30 is a layer between the insulating copper substrate 20 and the circuit layer 40 . The insulating layer 30 is formed of an insulating resin composition including an insulating resin 31 and an inorganic filler 32 . The insulating layer 30 is formed of an insulating resin composition including an insulating resin 31 with high insulating properties and an inorganic filler 32 with high thermal conductivity, so that the insulating properties can be maintained, and the distance from the circuit layer 40 to the copper substrate can be reduced. 20 is the thermal resistance of the copper base substrate 10 as a whole.

The insulating resin 31 preferably contains polyimide resin, polyimide resin, or a mixture thereof. Since these resins are excellent in properties such as insulation, withstand voltage, chemical resistance, and mechanical properties, these properties of the copper base substrate 10 are improved.

The inorganic filler 32 preferably has an average particle diameter within a range of 0.1 μm or more and 20 μm or less. When the average particle diameter of the inorganic filler 32 is 0.1 μm or more, the thermal conductivity of the insulating layer 30 is improved. When the average particle diameter of the inorganic filler 32 is 20 μm or less, the withstand voltage of the insulating layer 30 is improved. In addition, when the average particle diameter of the inorganic filler 32 is within the above-mentioned range, it is difficult for the inorganic filler 32 to form aggregated particles, and the inorganic filler 32 is easily dispersed uniformly in the insulating resin 31 . The inorganic filler 32 does not form aggregated particles, and when it is dispersed in the insulating resin 31 as primary particles or fine particles close to it, the withstand voltage of the insulating layer 30 is improved. From the viewpoint of improving the thermal conductivity of the insulating layer 30 , the average particle diameter of the inorganic filler 32 is preferably in the range of 0.3 μm or more and 20 μm or less.

The content of the inorganic filler 32 in the insulating layer 30 is preferably in the range of not less than 50% by volume and not more than 85% by volume. When the content of the inorganic filler 32 is 50 vol % μm or more, the thermal conductivity of the insulating layer 30 is improved. On the other hand, when the content of the inorganic filler 32 is 85 vol % μm or less, the withstand voltage of the insulating layer 30 is improved. In addition, when the content of the inorganic filler 32 is within the above-mentioned range, the inorganic filler 32 can be easily dispersed uniformly in the insulating resin 31 . When the inorganic filler 32 is uniformly dispersed in the insulating resin 31, the mechanical strength of the insulating layer 30 is improved. From the viewpoint of improving the thermal conductivity of the insulating layer 30 , it is more preferable that the content of the inorganic filler 32 be within the range of 50 vol % or more and 80 vol % or less.

As the inorganic filler 32, alumina (Al ₂ O ₃ ) particles, alumina hydrate particles, aluminum nitride (AlN) particles, silica (SiO ₂ ) particles, silicon carbide (SiC) particles, titanium oxide ( TiO ₂ ) particles, boron nitride (BN) particles, and the like. Among these fillers, alumina particles are preferred. The alumina particles are preferably α-alumina particles, and the ratio of the α-alumina particles to the true density (knock density/true density) is preferably 0.1 or more. The tap density/true density is related to the packing density of the α-alumina particles in the insulating layer 30 . When the tap density/true density is high, the packing density of the α-alumina particles in the insulating layer 30 can be increased. When the packing density of the α-alumina particles in the insulating layer 30 is high, the interval between the α-alumina particles in the insulating layer 30 is narrowed, and it is difficult to generate voids (air holes) in the insulating layer 30 . The tap tightness/true density is preferably in the range of 0.2 or more and 0.9 or less. In addition, α-alumina-based particles may be polycrystalline particles, but monocrystalline particles are more preferred.

The ratio (thickness/elastic modulus) of the insulating layer 30 to the thickness (unit: μm) of the elastic modulus (unit: GPa) at 100° C. is 50 or more. Since the thickness/elasticity modulus of the insulating layer 30 is as high as 50 or more, the insulating layer 30 is easily deformed, and the cushioning property in the thickness direction becomes high. Therefore, the function of the insulating layer 30 to alleviate the difference between the thermal expansion coefficients of the copper substrate 20 and the circuit layer 40 caused by the cooling and heating cycle is increased. The thickness/elastic modulus of the insulating layer 30 is preferably within the range of 50 or more and 20,000 or less, preferably within the range of 50 or more and 2,000 or less, and more preferably within the range of 50 or more and 200 or less. The elastic modulus of the insulating layer 30 at 100° C. is preferably in the range of 0.01GPa or more and 1GPa or less, and more preferably in the range of 0.01GPa or more and 0.1GPa or less. Further, the thickness of the insulating layer 30 is preferably within a range of 10 μm or more and 200 μm or less, and more preferably within a range of 50 μm or more and 200 μm or less.

The circuit layer 40 is formed in a circuit pattern shape. On the circuit layer 40 formed in this circuit pattern shape, the terminal 61 of the electronic component 60 is joined by solder 50 or the like. As the material of the circuit layer 40, metals such as copper, copper alloy, aluminum, aluminum alloy, and gold can be used. The circuit layer 40 is preferably made of copper foil, copper alloy foil, aluminum foil or aluminum alloy foil.

The elastic modulus of the circuit layer 40 at 100° C. is less than 100 GPa, so the stress added to the solder due to the difference in thermal expansion rate between the circuit layer 40 and the electronic component 60 caused by the cooling and heating cycle can be reduced. The elastic modulus of the circuit layer 40 at 100° C. is preferably in the range of 50 GPa or more and 100 GPa or less. The thickness of the circuit layer 40 is preferably in the range of not less than 20 μm and not more than 200 μm.

The thicknesses of the copper substrate 20 , the insulating layer 30 , and the circuit layer 40 of the copper base substrate 10 can be measured, for example, as follows. The copper base substrate 10 is embedded in resin, and the cross section is exposed by mechanical polishing. Next, the exposed cross section of the copper base substrate was observed with an optical microscope, and the thicknesses of the copper substrate 20 , the insulating layer 30 and the circuit layer 40 were measured.

The elastic modulus of the copper substrate 20, the insulating layer 30, and the circuit layer 40 of the copper base substrate 10 is a value measured at 100°C. The elastic modulus (tensile elastic modulus) of the copper substrate 20 and the circuit layer 40 of the copper base substrate 10 can be measured, for example, as follows. The insulating layer 30 of the copper base substrate 10 is removed through a solvent, and the copper substrate 20 and the circuit layer 40 are separated. The elastic modulus of the obtained copper substrate 20 and circuit layer 40 was measured by dynamic viscoelasticity measurement. The elastic modulus of the insulating layer 30 of the copper base substrate 10 can be measured, for example, as follows. The copper substrate 20 and the circuit layer 40 of the copper base substrate 10 are removed by etching, and the insulating layer 30 is isolated. The elastic modulus of the obtained insulating layer 30 was measured by dynamic viscoelasticity measurement.

Examples of the electronic components 60 mounted on the copper base substrate 10 of the present embodiment are not particularly limited, and examples thereof include semiconductor elements, resistors, capacitors, and crystal oscillators. Examples of semiconductor elements include MOSFET (Metal-oxide-semiconductor field effect transistor), IGBT (Insulated Gate Bipolar Transistor), LSI (Large Scale Integration), LED (Light Emitting Diode), LED chip, LED-CSP (LED-Chip Size Package).

Hereinafter, the manufacturing method of the copper base board|substrate 10 concerning this embodiment is demonstrated. The copper base substrate 10 of the present embodiment can be manufactured by a method including, for example, an insulating layer formation process and a circuit lamination process.

In the insulating layer forming process, an insulating layer 30 is formed on the copper substrate 20, and a copper substrate with an insulating layer is obtained. The thickness (unit: μm) of the insulating layer 30 is obtained by forming the insulating layer 30 for elastic modulus measurement on the copper substrate 20, measuring the elastic modulus of the obtained insulating layer 30, and setting the thickness/elasticity modulus to a thickness of 50 or more. As a method of forming the insulating layer 30, a coating method or an electrodeposition method can be used.

The coating method is a method of coating a coating liquid containing a solvent, an insulating resin and an inorganic filler on the copper substrate 20 to form a coating layer, and then heating the coating layer to obtain the insulating layer 30 . As the coating liquid, an inorganic filler-dispersed resin material solution containing a resin material solution in which the insulating resin is dissolved and an inorganic filler dispersed in the resin material solution can be used. As a method of applying the coating liquid to the surface of the substrate, spin coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, and immersion coating can be used. Buffa, etc.

The electrodeposition method is to immerse the copper substrate 20 in an electrodeposition solution containing insulating resin particles and inorganic fillers, electrodeposit insulating resin particles and inorganic fillers on the surface of the substrate to form an electrodeposited film, and then heat the obtained electrodeposited film to form insulating The method of layer 30. As an electrodeposition solution, it can be used in an inorganic filler-dispersed resin material solution containing an insulating resin material solution and an inorganic filler dispersed in the insulating resin solution, adding a weak solvent for the insulating resin material, and using the insulating resin as a Particles are prepared by precipitation.

In the circuit lamination process, metal foil is laminated on the insulating layer 30 of the copper substrate with the insulating layer, and the resulting laminate is heated and pressed to form the circuit layer 40 , and the copper base substrate 10 is obtained. The heating temperature of the laminate is, for example, 200°C or higher, more preferably 250°C or higher. The upper limit of the heating temperature is less than the thermal decomposition temperature of the insulating resin, and is preferably a temperature 30°C lower than the thermal decomposition temperature. The pressure applied at the time of crimping is within the range of 1 MPa or more and 30 MPa or less, and more preferably within the range of 3 MPa or more and 25 MPa or less. The crimping time varies depending on the heating temperature and pressure, but generally it is 10 minutes or more and 180 minutes or less.

According to the copper base substrate 10 of the present embodiment configured as above, the insulating layer 30 has an elastic modulus (unit: GPa) at 100° C. (unit: GPa) with a thickness (unit: μm) ratio of 50 or more. It is easy to deform, and the difference in thermal expansion rate between the copper substrate 20 and the circuit layer 40 caused by the cooling and heating cycle can be alleviated by the insulating layer 30 . In addition, since the elastic modulus of the circuit layer 40 at 100° C. is as low as 100 GPa or less, the difference between the thermal expansion coefficients of the circuit layer 40 and the electronic component 60 caused by the cycle of cooling and heating can be reduced. Therefore, the stress applied to the solder 50 for joining the electronic component 60 and the circuit layer 40 of the copper base substrate 10 can be reduced through the cooling and heating cycle. Therefore, the copper base substrate 10 of the present embodiment improves the reliability with respect to the cooling and heating cycle when the electronic component 60 is mounted.

In addition, in the copper base substrate 10 of the present embodiment, when the insulating layer 30 contains polyimide resin, polyimide resin, or a mixture thereof, the insulating properties, withstand voltage, etc. of the copper base substrate 10 are improved. Chemical resistance and mechanical properties. Furthermore, the insulating layer 30 includes the inorganic filler 32 . When the average particle size of the inorganic filler 32 is in the range of 0.1 μm to 20 μm, the thermal conductivity and withstand voltage of the copper base substrate 10 are improved. Furthermore, when the circuit layer 40 is made of copper foil, copper alloy foil, aluminum foil, or aluminum alloy foil, the thickness of the circuit layer 40 can be reduced due to high conductivity.

The embodiments of the present invention have been described above, but the present invention is not limited thereto, and changes can be appropriately made without departing from the technical idea of the invention. [Example]

[Example 1 of the present invention] Solvent-soluble polyimide solution and α-alumina powder (crystal structure: single crystal, average particle diameter: 0.7 μm), polyimide and α-oxidation in the solid (insulating layer) generated by heating The content ratio of the aluminum powder was 65% by volume and mixed. A solvent was added to the obtained mixture so that the concentration of polyimide was 5% by mass and diluted. Next, the obtained diluted mixture was subjected to a dispersion treatment by repeating 10 times of high-pressure spray treatment at a pressure of 50 MPa using a Star Burst manufactured by Sugino Machinery Co., Ltd. to prepare a coating liquid for forming an insulating layer.

A copper substrate (composition: C1100, tough copper) having a thickness of 1000 μm and a length of 30 mm x a width of 20 mm was prepared. On the surface of the copper substrate, a coating liquid for forming an insulating layer is applied by a bar coating method to form a coating layer. Next, the copper substrate on which the coating layer was formed was placed on a hot plate, and the temperature was raised from room temperature to 60°C at 3°C/min. After heating at 60°C for 100 minutes, the temperature was further increased to 1°C/min. The coating layer was dried by heating at 120°C for 100 minutes. Next, after heating the copper substrate at 250° C. for 1 minute, it was heated at 400° C. for 1 minute. In this way, on the surface, an insulating film-attached copper substrate in which an insulating layer made of a polyimide resin in which α-alumina single crystal particles are dispersed was formed was produced. However, the thickness of the insulating layer is 30 μm, the elastic modulus at 100° C. is 0.27 GPa, and the thickness/elastic modulus is 110.

On the insulating film of the obtained copper substrate with an insulating layer, a copper foil with a thickness of 70 μm (elastic modulus at 100° C.: 75 GPa, GHY5-HA-V2 manufactured by JX Metals Co., Ltd.) was laminated. Next, using a carbon jig, the obtained laminate was heated in a vacuum at a pressure-bonding temperature of 300° C. for 120 minutes while applying a pressure of 5 MPa, and the insulating layer and the copper foil were pressure-bonded. In this way, a copper base substrate in which a copper substrate and an insulating layer and a copper foil are laminated in this order is produced.

[Examples 2 to 4 of the present invention, Comparative Examples 1 to 2] A copper base substrate was produced in the same manner as in Example 1 of the present invention, except that the thickness and elastic modulus of the insulating layer and the elastic modulus of the circuit layer were changed to the values described in Table 1 below.

[evaluate] With respect to the copper base substrates obtained in Examples 1 to 4 of the present invention and Comparative Examples 1 to 2, the reliability of the cooling and heating cycle was evaluated by the following method. The results are shown in Table 1.

(Cold/hot cycle reliability for copper base substrates) On the circuit layer of the copper base substrate, apply Sn-Ag-Cu solder to form a solder layer with a length of 2.5cm × a width of 2.5cm × a thickness of 100μm. On the solder layer, a 2.5cm square Si wafer is mounted to make a test. body. For the produced test body, 3000 cycles were assigned to one cycle of cooling and heating cycles of -40°C x 30 minutes to 150°C x 30 minutes. The test body after applying the cooling and heating cycle is embedded in the resin, and the sample whose cross section is exposed by grinding is used to observe it. In the solder layer, those with a length of 5 mm or more are designated as "0", and those with a length of 5 mm or more are generated. "X".

The ratio (thickness/elasticity) of the elastic modulus (unit: GPa) of the insulating layer to the thickness (unit: μm) and the elastic modulus of the circuit layer are within the scope of the present invention for the copper base substrates of Examples 1 to 4 of the present invention It was confirmed that the reliability with respect to the cooling and heating cycle was excellent. This is because the thickness/elastic modulus of the insulating layer is within the scope of the present invention, and the difference in thermal expansion rate between the copper substrate and the electronic components caused by the cooling and heating cycle can be alleviated by the insulating layer. In addition, the thermal stress imparted to the solder due to the difference in thermal expansion coefficient between the circuit layer and the electronic component can be reduced through the elastic modulus of the circuit layer within the scope of the present invention.

Compared with this, although the elastic modulus thickness/elastic modulus of the insulating layer is within the scope of the present invention, the copper base substrate of Comparative Example 1 in which the elastic modulus of the circuit layer exceeds the scope of the present invention is less reliable for cooling and heating cycles . This is because the thermal stress imparted to the solder due to the difference in thermal expansion coefficients between the circuit layer and the electronic component increases due to the fact that the elastic modulus of the circuit layer exceeds the scope of the present invention.

In addition, although the elastic modulus of the circuit layer is within the scope of the present invention, the copper base substrate of Comparative Example 2 in which the thickness/elastic modulus of the insulating layer is not within the scope of the present invention is less reliable for cooling and heating cycles. This is because the thickness/elastic modulus of the insulating layer is not within the scope of the present invention, and the thermal stress imparted to the solder by the difference in thermal expansion rate between the copper substrate and the circuit layer caused by the cooling and heating cycle cannot be sufficiently relieved.

10: Copper base substrate 20: Copper substrate 30: Insulation layer 31: Insulating resin 32: inorganic filler 40: circuit layer 50: Solder 60: Electronic Parts 61: Terminal

1 is a schematic cross-sectional view of a copper base substrate according to an embodiment of the present invention.

10: Copper base substrate

20: Copper substrate

30: Insulation layer

31: Insulating resin

32: inorganic filler

40: circuit layer

50: Solder

60: Electronic Parts

61: Terminal

Claims (4)

A copper base substrate comprising a copper base substrate, an insulating layer, and a circuit layer laminated in this order, characterized by: The ratio of the thickness (unit: μm) of the insulating layer to the elastic modulus (unit: GPa) at 100°C is 50 or more, The elastic modulus of the circuit layer at 100° C. is 100 GPa or less. The copper base substrate according to claim 1, wherein the insulating layer is a resin containing polyimide resin, polyimide resin, or a mixture thereof. The copper base substrate according to claim 1 or 2, wherein the insulating layer contains an inorganic filler, and the average particle diameter of the inorganic filler is within a range of 0.1 μm or more and 20 μm or less. The copper base substrate according to any one of claims 1 to 3, wherein the circuit layer is made of copper foil, copper alloy foil, aluminum foil, or aluminum alloy foil.

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